LA

Question 1

Briefly explain the process of depolarization

Answer 1

Na+ enters cell, K+ leaves cell

Question 2

What is the mode of action of LA agents:

a) Alter resting potential of cell membrane
b) Alter threshold potential
c) Decrease rate of depolarization
d) Prolonging the phase of depolarization

Answer 2

c) Decrease the rate of depolarization to a level which becomes too slow to reach threshold of action potential

Question 3

Which is able to diffuse across membrane:

a) ionic particles
b) Non-ionic particles

Answer 3

Non ionic

Question 4

The preferred LAs used in clinical practices are

a) Esters
b) Amides

Answer 4

b) Amides

Question 5

Which of these does not contain adrenaline

a) Lignocaine
b) Mepivacaine
c) Prilocaine
d) Articaine

Answer 5

Prilocaine

Question 6

Where is Articaine metabolised?

Answer 6

Liver and Plasma

Question 7

Duration of Lignocaine with Adrenaline:

Answer 7

60-90 mins

Question 8

Lignocaine is excreted by the:

Answer 8

Kidneys

Question 10

What is the spposed advantage of mepivacaine over lignocaine?

Answer 10

Longer lasting as less vasodilator effect

Question 11

Priolocaine is metabolised in the and excreted in.

Answer 11

Lungs and Liver

Urine

Question 12

Prilocaine is implicated in the formation of:

It is therefore contraindicated in:

Answer 12

Methaemaglobin

Pregnant

Question 13

What is used to reverese methamaglobinaemia

Answer 13

Methylene blue

Question 14

Why is articaine thought to be less toxic than lignocaine?

Answer 14

Shorter half life

Question 15

Articaie is not recommended for whom:

Answer 15

• Pregnant
• Under 4
• Sulphur allergy
• Pseudocholinesterase deficiency
• Methaemogobinaemia

Question 16

Articaine is metabolised by:

Answer 16

Liver, lung, plasma

Question 17

Which is not used in routine dentistry:

a) Mepivacaine
b) Articaine
c) Bupivicaine
d) Lignocaine

Answer 17

c) Bupivacaine

Question 18

How is LA dosage calculated?

Answer 18

LA% x cartridge volume x 10

Question 19

What is the absolute maximum safe dose of Lignocaine

Answer 19

500mg

Question 20

What is the absolute maximum safe dose of articaine?

Answer 20

700mg

Question 21

What is the maximum recommended safe dose of Lignocaine per kg body weight:

Answer 21

7.0mg

Question 22

Adrenaline is a

a) Bronchoconstrictor
b) Bronchodilator

Answer 22

b) Bronchodilator

Question 23

What effects does adrenaline have on the heart

Answer 23

• Increase rate and contractility eg cardiac output
• Increased workload and oxygen demand
• May induce angina or arrhythmias in susceptible patients
• May also increase blood pressure
• MUST USE PRECAUTION if someone is being prescribed non-selective beta blockers

Question 24

The maximum recommended adrenaline dose for healthy patients is:

Answer 24

0.2mg

Question 25

Maximum recommended dose of LA for cardiac patients is:

Answer 25

2x 2.2ml cartridges

Question 26

Adrenaline in LA may interact with what drugs:

Answer 26

* MAOIs * TCAs

Question 27

Is it prilocaine or felylpressin which is an issue for pregnant women

Answer 27

prilocaine

Question 28

what is the recommended needle gauge

Answer 28

27g

Question 29

What conditions should patients not be reclined

Answer 29

Heart failure Third trimester pregnancy

Question 30

Why are posterior superior alveolar nerve blocks not recommended?

Answer 30

Pterygoid venous plexus in this location, risk of haematoma and cavernous sinus thrombosis

Question 31

What nerve supplies the buccal mucosa of the lower incisors, canines and premolars?

Answer 31

Mental nerve

Question 32

What nerve supplies the buccal mucosa to the first, second and third molars

Answer 32

Long buccal nerve block

Question 33

What space are IDBs injected into?

Answer 33

Pterygomandibular space

Question 34

What borders the pterygomandibular space superiorly

Answer 34

Lateral pterygoid muscle

Question 35

What borders the pterygomandibular space medially?

Answer 35

Medial pterygoid muscle

Question 36

What borders the pterygomandibular space posteriorly

Answer 36

Parotid gland

Question 37

What borders the pterygomandibular space anteriorly

Answer 37

Buccinator

Question 38

What is the volume of the pterygomandibular space?

Answer 38

2ml

Question 39

The pterygomandibular space is located in the lower part of the .

Answer 39

Infra-temporal fossa

Question 40

Which structure is not contained in the parotid gland a) Facial nerve b) External carotid artery c) Internal carotid artery d) Retromandibular vein

Answer 40

c) Internal carotid artery

Question 41

What attaches to the Pterygoid hamulus

Answer 41

* Buccinator * Superior pharyngeal constrictor

Question 42

When might a Periodontal ligament injection be the primary indication for LA

Answer 42

Patient has a bleeding problem

Question 43

When won't a periodontal ligament injection work

Answer 43

inflammation

Question 44

If a patient has had MI or heart failure in last 6 months, pain relief should be opted for over tx True or false

Answer 44

True

Question 46

5 complications of LA

Answer 46

* Failure to achieve LA * Local complications eg breakages * Overdose * Spread of infection * Allergic reaction * Pain, bruising, trismus, haematoma, lip biting, oedema

Question 47

What to do about persistent anesthesia or paraesthesia:

Answer 47

Usually resolves in 8 weeks, but in rare cases may be permanent. Discuss with maxfac if no improvement.

Question 48

5 causes of persistent anesthesia or paraesthesia following LA:

Answer 48

1. Trauma to nerve sheath eg barbed needles or hitting it 2. Contaminated LA 3. Oedema in the pterygomandibular space 4. LA toxic damage to nerve

Question 49

What might cause trismus following LA

Answer 49

* Trauma to the medial pterygoid muscles * Bleeding in the pterygomandibular space * Injection into the medial pterygoid * Contaminated LA or excessive volumes * Low grade infection

Question 50

MAangement of trismus following LA:

Answer 50

Reassure. Advise 5 days of rest then mouth opening exercise and advise use of sugar free chewing gum. If not improvement in 6 weeks, Maxfax referral

Question 51

What would cause a haematoma during LA

Answer 51

Inadvertent nicking of blood vessels Frequently seen in pts with haemostatic disorders or on blood thinning medications

Question 52

Management of haematoma if you see it immediately

Answer 52

Ice. Advice re trismus and discomfort. Apply heat form the following day

Question 53

Management for lip chewing injury:

Answer 53

* Analgesics * Lukewarm salt water/chlorhex rinse * Vaseline to minimize irritation * Instructions * Short acting LA next time

Question 54

How long will a facial nerve paralysis from LA last?

Answer 54

About 2 hours

Question 55

What might cause an ulcer at site of injection?

Answer 55

Apthous stomatitis or viral cause. Rare.

Question 56

What might cause blanching of the facial skin following LA

Answer 56

Injected into artery. Transient.

Question 57

What might cause a patient to become temporarily blind or blurred vision following LA

Answer 57

Abnormal anastomosis and injected into inferior dental artery. close to infra-orbital fissure

Question 58

Patient presents to clinic 3-4 hours following dental procedure, with central cyanosis and respiratory distress. You exo'd teeth under prilocaine. What might be the cause.

Answer 58

Overdose of Prilocaine (over 400mg) leading to methaemoglobinaemia (can also happen with benzocaine overdose)

Question 59

What is the safe total dose of lignocaine 2% per kg. body weight.

Answer 59

4.4mg per kg body weight

Question 60

What is the max safe dose of lignocaine 2%

Answer 60

300mg

Question 61

What is a hot tooth?

Answer 61

A tooth with pulp inflammation causing hyperalgesia